1. Field of the Invention
The present invention relates to nanostructures and, more specifically, to Sb-doped ZnO nanowires.
2. Description of the Related Art
Piezoelectric semiconductors with wurtzite or zinc blend structures such as ZnO, GaN, InN and ZnS have attracted increased attention in the burgeoning field of piezotronics and piezo-phototronics, which can be attributed to their numerous robust synthesis methods and potential for realizing novel applications by coupling their piezoelectric and semiconductor properties. The working principle of piezotronics lies in the modulation/gating of carrier transport across the barriers/junctions through piezoelectric-polarization-induced electric field (piezopotential) under strain, which is known as the piezotronic effect. This provides a new mechanism for controlling charge carrier transport by mechanical strain in addition to the well-known electrically-induced “field-effect.” A wide variety of novel applications based on the piezotronic effect have been demonstrated including strain sensors, logic units, memory cells, electrochemical devices, and tactile imaging arrays. However, the aforementioned piezotronic devices were all fabricated using intrinsically n-type ZnO and few studies of piezotronics based on p-type materials, especially p-type ZnO have been done. In order to develop a full understanding of the theory of piezotronics, and enable novel applications in electronics, optoelectronics, smart MEMS/NEMS and human-machine interfacing it is important to investigate the feasibility of p-type piezoelectric semiconductors for piezotronic applications.
Different types of p-type doping in ZnO nanowires has been previously achieved through a variety of methods including chemical vapor deposition and pulsed laser deposition. However, the doping often suffers from poor stability due to the formation of low energy donor impurities such as hydrogen interstitials and oxygen vacancies (VO). Group I elements in the Zn site should act as acceptors, but have been shown to form interstitials due to their small atomic radii, making them act as donors instead. Of the group V elements, nitrogen has often been considered the most promising candidate for achieving stable p-type doped ZnO due to its similar atomic radius to oxygen. However, there has been difficulty in reproducing them. Despite their much larger atomic radii, arsenic (As) and antimony (Sb) have both been demonstrated as promising candidates for p-type doping in ZnO. Rather than occupying an O site, it has been suggested that an As/SbZn-2VZn complex forms. Recently, p-type ZnO nanowires doped with Sb were demonstrated through low-temperature solution-phase process, using a glycolate ligand to control the release rate of dopant. However, those solution-grown nanowires were only a few μm in length, making manipulation and further experimentation difficult.
Therefore, there is a need for a method of growing p-type doped nanowires that are longer and more stable.